1. Technical Field
The present invention relates to an apparatus and method for applying at least one elastic strand onto a moving substrate web along a curved path. More particularly, the present invention relates to an apparatus and method for applying elastic strands in a curved configuration at each of the leg opening regions of a disposable absorbent article, such as a disposable diaper.
2. Description of the Related Art
Absorbent articles, such as disposable diapers, training pants, adult incontinence articles and the like, have incorporated elasticized gathers at the leg openings of the article to help contain body exudates. The leg openings are positioned at the lateral side margins of the article and can be elasticized with a single elastic member or with multiple elastic members. Various techniques for applying multiple elastic strands onto a substrate are well known to those skilled in the art.
It has been desirable to employ elastic members which are curved to better follow the contours of the leg openings formed in the side margins of disposable absorbent articles. The curved elastic members improve the ability of the article to contain body exudates. Various techniques for applying curved elastic members onto a substrate are well known to those skilled in the art. For example, techniques for applying an elastic member to a substrate web along a curved pattern have been described in U.S. Pat. No. 4,915,676 issued Apr. 10, 1990, to Rajala et al. and U.S. Pat. No. 5,275,676 issued Jan. 4, 1994, to Rooyakkers et al.
However, some conventional techniques for applying curved elastic members, such as described above, have not provided an adequate system for efficiently placing an elastic member along a desired curvilinear path on the surface of a moving substrate. Typically, conventional techniques have incorporated complicated web paths for the elastic members which include oscillations of great magnitude such that the desired curvature can be maintained. Moreover, conventional techniques have not adequately maintained the desired spacing between the individual elastic strands when multiple strands of elastomeric material are applied to a substrate web along a curvilinear path. Further, the complicated web paths of conventional techniques have not provided an efficient method to thread the elastic members.